/*
 * Copyright (C) 2003-2004 The FFmpeg project
 * Copyright (C) 2019 Peter Ross
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * On2 VP3/VP4 Video Decoder
 *
 * VP3 Video Decoder by Mike Melanson (mike at multimedia.cx)
 * For more information about the VP3 coding process, visit:
 *   http://wiki.multimedia.cx/index.php?title=On2_VP3
 *
 * Theora decoder by Alex Beregszaszi
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "libavutil/imgutils.h"

#include "avcodec.h"
#include "get_bits.h"
#include "hpeldsp.h"
#include "internal.h"
#include "mathops.h"
#include "thread.h"
#include "videodsp.h"
#include "vp3data.h"
#include "vp4data.h"
#include "vp3dsp.h"
#include "xiph.h"

#define FRAGMENT_PIXELS 8

// FIXME split things out into their own arrays
typedef struct Vp3Fragment {
    int16_t dc;
    uint8_t coding_method;
    uint8_t qpi;
} Vp3Fragment;

#define SB_NOT_CODED        0
#define SB_PARTIALLY_CODED  1
#define SB_FULLY_CODED      2

// This is the maximum length of a single long bit run that can be encoded
// for superblock coding or block qps. Theora special-cases this to read a
// bit instead of flipping the current bit to allow for runs longer than 4129.
#define MAXIMUM_LONG_BIT_RUN 4129

#define MODE_INTER_NO_MV      0
#define MODE_INTRA            1
#define MODE_INTER_PLUS_MV    2
#define MODE_INTER_LAST_MV    3
#define MODE_INTER_PRIOR_LAST 4
#define MODE_USING_GOLDEN     5
#define MODE_GOLDEN_MV        6
#define MODE_INTER_FOURMV     7
#define CODING_MODE_COUNT     8

/* special internal mode */
#define MODE_COPY             8

static int theora_decode_header(AVCodecContext *avctx, GetBitContext *gb);
static int theora_decode_tables(AVCodecContext *avctx, GetBitContext *gb);


/* There are 6 preset schemes, plus a free-form scheme */
static const int ModeAlphabet[6][CODING_MODE_COUNT] = {
    /* scheme 1: Last motion vector dominates */
    { MODE_INTER_LAST_MV,    MODE_INTER_PRIOR_LAST,
      MODE_INTER_PLUS_MV,    MODE_INTER_NO_MV,
      MODE_INTRA,            MODE_USING_GOLDEN,
      MODE_GOLDEN_MV,        MODE_INTER_FOURMV },

    /* scheme 2 */
    { MODE_INTER_LAST_MV,    MODE_INTER_PRIOR_LAST,
      MODE_INTER_NO_MV,      MODE_INTER_PLUS_MV,
      MODE_INTRA,            MODE_USING_GOLDEN,
      MODE_GOLDEN_MV,        MODE_INTER_FOURMV },

    /* scheme 3 */
    { MODE_INTER_LAST_MV,    MODE_INTER_PLUS_MV,
      MODE_INTER_PRIOR_LAST, MODE_INTER_NO_MV,
      MODE_INTRA,            MODE_USING_GOLDEN,
      MODE_GOLDEN_MV,        MODE_INTER_FOURMV },

    /* scheme 4 */
    { MODE_INTER_LAST_MV,    MODE_INTER_PLUS_MV,
      MODE_INTER_NO_MV,      MODE_INTER_PRIOR_LAST,
      MODE_INTRA,            MODE_USING_GOLDEN,
      MODE_GOLDEN_MV,        MODE_INTER_FOURMV },

    /* scheme 5: No motion vector dominates */
    { MODE_INTER_NO_MV,      MODE_INTER_LAST_MV,
      MODE_INTER_PRIOR_LAST, MODE_INTER_PLUS_MV,
      MODE_INTRA,            MODE_USING_GOLDEN,
      MODE_GOLDEN_MV,        MODE_INTER_FOURMV },

    /* scheme 6 */
    { MODE_INTER_NO_MV,      MODE_USING_GOLDEN,
      MODE_INTER_LAST_MV,    MODE_INTER_PRIOR_LAST,
      MODE_INTER_PLUS_MV,    MODE_INTRA,
      MODE_GOLDEN_MV,        MODE_INTER_FOURMV },
};

static const uint8_t hilbert_offset[16][2] = {
    { 0, 0 }, { 1, 0 }, { 1, 1 }, { 0, 1 },
    { 0, 2 }, { 0, 3 }, { 1, 3 }, { 1, 2 },
    { 2, 2 }, { 2, 3 }, { 3, 3 }, { 3, 2 },
    { 3, 1 }, { 2, 1 }, { 2, 0 }, { 3, 0 }
};

enum {
    VP4_DC_INTRA  = 0,
    VP4_DC_INTER  = 1,
    VP4_DC_GOLDEN = 2,
    NB_VP4_DC_TYPES,
    VP4_DC_UNDEFINED = NB_VP4_DC_TYPES
};

static const uint8_t vp4_pred_block_type_map[8] = {
    [MODE_INTER_NO_MV]      = VP4_DC_INTER,
    [MODE_INTRA]            = VP4_DC_INTRA,
    [MODE_INTER_PLUS_MV]    = VP4_DC_INTER,
    [MODE_INTER_LAST_MV]    = VP4_DC_INTER,
    [MODE_INTER_PRIOR_LAST] = VP4_DC_INTER,
    [MODE_USING_GOLDEN]     = VP4_DC_GOLDEN,
    [MODE_GOLDEN_MV]        = VP4_DC_GOLDEN,
    [MODE_INTER_FOURMV]     = VP4_DC_INTER,
};

typedef struct {
    int dc;
    int type;
} VP4Predictor;

#define MIN_DEQUANT_VAL 2

typedef struct Vp3DecodeContext {
    AVCodecContext *avctx;
    int theora, theora_tables, theora_header;
    int version;
    int width, height;
    int chroma_x_shift, chroma_y_shift;
    ThreadFrame golden_frame;
    ThreadFrame last_frame;
    ThreadFrame current_frame;
    int keyframe;
    uint8_t idct_permutation[64];
    uint8_t idct_scantable[64];
    HpelDSPContext hdsp;
    VideoDSPContext vdsp;
    VP3DSPContext vp3dsp;
    DECLARE_ALIGNED(16, int16_t, block)[64];
    int flipped_image;
    int last_slice_end;
    int skip_loop_filter;

    int qps[3];
    int nqps;
    int last_qps[3];

    int superblock_count;
    int y_superblock_width;
    int y_superblock_height;
    int y_superblock_count;
    int c_superblock_width;
    int c_superblock_height;
    int c_superblock_count;
    int u_superblock_start;
    int v_superblock_start;
    unsigned char *superblock_coding;

    int macroblock_count; /* y macroblock count */
    int macroblock_width;
    int macroblock_height;
    int c_macroblock_count;
    int c_macroblock_width;
    int c_macroblock_height;
    int yuv_macroblock_count; /* y+u+v macroblock count */

    int fragment_count;
    int fragment_width[2];
    int fragment_height[2];

    Vp3Fragment *all_fragments;
    int fragment_start[3];
    int data_offset[3];
    uint8_t offset_x;
    uint8_t offset_y;
    int offset_x_warned;

    int8_t (*motion_val[2])[2];

    /* tables */
    uint16_t coded_dc_scale_factor[2][64];
    uint32_t coded_ac_scale_factor[64];
    uint8_t base_matrix[384][64];
    uint8_t qr_count[2][3];
    uint8_t qr_size[2][3][64];
    uint16_t qr_base[2][3][64];

    /**
     * This is a list of all tokens in bitstream order. Reordering takes place
     * by pulling from each level during IDCT. As a consequence, IDCT must be
     * in Hilbert order, making the minimum slice height 64 for 4:2:0 and 32
     * otherwise. The 32 different tokens with up to 12 bits of extradata are
     * collapsed into 3 types, packed as follows:
     *   (from the low to high bits)
     *
     * 2 bits: type (0,1,2)
     *   0: EOB run, 14 bits for run length (12 needed)
     *   1: zero run, 7 bits for run length
     *                7 bits for the next coefficient (3 needed)
     *   2: coefficient, 14 bits (11 needed)
     *
     * Coefficients are signed, so are packed in the highest bits for automatic
     * sign extension.
     */
    int16_t *dct_tokens[3][64];
    int16_t *dct_tokens_base;
#define TOKEN_EOB(eob_run)              ((eob_run) << 2)
#define TOKEN_ZERO_RUN(coeff, zero_run) (((coeff) * 512) + ((zero_run) << 2) + 1)
#define TOKEN_COEFF(coeff)              (((coeff) * 4) + 2)

    /**
     * number of blocks that contain DCT coefficients at
     * the given level or higher
     */
    int num_coded_frags[3][64];
    int total_num_coded_frags;

    /* this is a list of indexes into the all_fragments array indicating
     * which of the fragments are coded */
    int *coded_fragment_list[3];

    int *kf_coded_fragment_list;
    int *nkf_coded_fragment_list;
    int num_kf_coded_fragment[3];

    VLC dc_vlc[16];
    VLC ac_vlc_1[16];
    VLC ac_vlc_2[16];
    VLC ac_vlc_3[16];
    VLC ac_vlc_4[16];

    VLC superblock_run_length_vlc; /* version < 2 */
    VLC fragment_run_length_vlc; /* version < 2 */
    VLC block_pattern_vlc[2]; /* version >= 2*/
    VLC mode_code_vlc;
    VLC motion_vector_vlc; /* version < 2 */
    VLC vp4_mv_vlc[2][7]; /* version >=2 */

    /* these arrays need to be on 16-byte boundaries since SSE2 operations
     * index into them */
    DECLARE_ALIGNED(16, int16_t, qmat)[3][2][3][64];     ///< qmat[qpi][is_inter][plane]

    /* This table contains superblock_count * 16 entries. Each set of 16
     * numbers corresponds to the fragment indexes 0..15 of the superblock.
     * An entry will be -1 to indicate that no entry corresponds to that
     * index. */
    int *superblock_fragments;

    /* This is an array that indicates how a particular macroblock
     * is coded. */
    unsigned char *macroblock_coding;

    uint8_t *edge_emu_buffer;

    /* Huffman decode */
    int hti;
    unsigned int hbits;
    int entries;
    int huff_code_size;
    uint32_t huffman_table[80][32][2];

    uint8_t filter_limit_values[64];
    DECLARE_ALIGNED(8, int, bounding_values_array)[256 + 2];

    VP4Predictor * dc_pred_row; /* dc_pred_row[y_superblock_width * 4] */
} Vp3DecodeContext;

/************************************************************************
 * VP3 specific functions
 ************************************************************************/

static av_cold void free_tables(AVCodecContext *avctx)
{
    Vp3DecodeContext *s = avctx->priv_data;

    av_freep(&s->superblock_coding);
    av_freep(&s->all_fragments);
    av_freep(&s->nkf_coded_fragment_list);
    av_freep(&s->kf_coded_fragment_list);
    av_freep(&s->dct_tokens_base);
    av_freep(&s->superblock_fragments);
    av_freep(&s->macroblock_coding);
    av_freep(&s->dc_pred_row);
    av_freep(&s->motion_val[0]);
    av_freep(&s->motion_val[1]);
}

static void vp3_decode_flush(AVCodecContext *avctx)
{
    Vp3DecodeContext *s = avctx->priv_data;

    if (s->golden_frame.f)
        ff_thread_release_buffer(avctx, &s->golden_frame);
    if (s->last_frame.f)
        ff_thread_release_buffer(avctx, &s->last_frame);
    if (s->current_frame.f)
        ff_thread_release_buffer(avctx, &s->current_frame);
}

static av_cold int vp3_decode_end(AVCodecContext *avctx)
{
    Vp3DecodeContext *s = avctx->priv_data;
    int i, j;

    free_tables(avctx);
    av_freep(&s->edge_emu_buffer);

    s->theora_tables = 0;

    /* release all frames */
    vp3_decode_flush(avctx);
    av_frame_free(&s->current_frame.f);
    av_frame_free(&s->last_frame.f);
    av_frame_free(&s->golden_frame.f);

    for (i = 0; i < 16; i++) {
        ff_free_vlc(&s->dc_vlc[i]);
        ff_free_vlc(&s->ac_vlc_1[i]);
        ff_free_vlc(&s->ac_vlc_2[i]);
        ff_free_vlc(&s->ac_vlc_3[i]);
        ff_free_vlc(&s->ac_vlc_4[i]);
    }

    ff_free_vlc(&s->superblock_run_length_vlc);
    ff_free_vlc(&s->fragment_run_length_vlc);
    ff_free_vlc(&s->mode_code_vlc);
    ff_free_vlc(&s->motion_vector_vlc);

    for (j = 0; j < 2; j++)
        for (i = 0; i < 7; i++)
            ff_free_vlc(&s->vp4_mv_vlc[j][i]);

    for (i = 0; i < 2; i++)
        ff_free_vlc(&s->block_pattern_vlc[i]);
    return 0;
}

/**
 * This function sets up all of the various blocks mappings:
 * superblocks <-> fragments, macroblocks <-> fragments,
 * superblocks <-> macroblocks
 *
 * @return 0 is successful; returns 1 if *anything* went wrong.
 */
static int init_block_mapping(Vp3DecodeContext *s)
{
    int sb_x, sb_y, plane;
    int x, y, i, j = 0;

    for (plane = 0; plane < 3; plane++) {
        int sb_width    = plane ? s->c_superblock_width
                                : s->y_superblock_width;
        int sb_height   = plane ? s->c_superblock_height
                                : s->y_superblock_height;
        int frag_width  = s->fragment_width[!!plane];
        int frag_height = s->fragment_height[!!plane];

        for (sb_y = 0; sb_y < sb_height; sb_y++)
            for (sb_x = 0; sb_x < sb_width; sb_x++)
                for (i = 0; i < 16; i++) {
                    x = 4 * sb_x + hilbert_offset[i][0];
                    y = 4 * sb_y + hilbert_offset[i][1];

                    if (x < frag_width && y < frag_height)
                        s->superblock_fragments[j++] = s->fragment_start[plane] +
                                                       y * frag_width + x;
                    else
                        s->superblock_fragments[j++] = -1;
                }
    }

    return 0;  /* successful path out */
}

/*
 * This function sets up the dequantization tables used for a particular
 * frame.
 */
static void init_dequantizer(Vp3DecodeContext *s, int qpi)
{
    int ac_scale_factor = s->coded_ac_scale_factor[s->qps[qpi]];
    int i, plane, inter, qri, bmi, bmj, qistart;

    for (inter = 0; inter < 2; inter++) {
        for (plane = 0; plane < 3; plane++) {
            int dc_scale_factor = s->coded_dc_scale_factor[!!plane][s->qps[qpi]];
            int sum = 0;
            for (qri = 0; qri < s->qr_count[inter][plane]; qri++) {
                sum += s->qr_size[inter][plane][qri];
                if (s->qps[qpi] <= sum)
                    break;
            }
            qistart = sum - s->qr_size[inter][plane][qri];
            bmi     = s->qr_base[inter][plane][qri];
            bmj     = s->qr_base[inter][plane][qri + 1];
            for (i = 0; i < 64; i++) {
                int coeff = (2 * (sum     - s->qps[qpi]) * s->base_matrix[bmi][i] -
                             2 * (qistart - s->qps[qpi]) * s->base_matrix[bmj][i] +
                             s->qr_size[inter][plane][qri]) /
                            (2 * s->qr_size[inter][plane][qri]);

                int qmin   = 8 << (inter + !i);
                int qscale = i ? ac_scale_factor : dc_scale_factor;
                int qbias = (1 + inter) * 3;
                s->qmat[qpi][inter][plane][s->idct_permutation[i]] =
                    (i == 0 || s->version < 2) ? av_clip((qscale * coeff) / 100 * 4, qmin, 4096)
                                               : (qscale * (coeff - qbias) / 100 + qbias) * 4;
            }
            /* all DC coefficients use the same quant so as not to interfere
             * with DC prediction */
            s->qmat[qpi][inter][plane][0] = s->qmat[0][inter][plane][0];
        }
    }
}

/*
 * This function initializes the loop filter boundary limits if the frame's
 * quality index is different from the previous frame's.
 *
 * The filter_limit_values may not be larger than 127.
 */
static void init_loop_filter(Vp3DecodeContext *s)
{
    ff_vp3dsp_set_bounding_values(s->bounding_values_array, s->filter_limit_values[s->qps[0]]);
}

/*
 * This function unpacks all of the superblock/macroblock/fragment coding
 * information from the bitstream.
 */
static int unpack_superblocks(Vp3DecodeContext *s, GetBitContext *gb)
{
    int superblock_starts[3] = {
        0, s->u_superblock_start, s->v_superblock_start
    };
    int bit = 0;
    int current_superblock = 0;
    int current_run = 0;
    int num_partial_superblocks = 0;

    int i, j;
    int current_fragment;
    int plane;
    int plane0_num_coded_frags = 0;

    if (s->keyframe) {
        memset(s->superblock_coding, SB_FULLY_CODED, s->superblock_count);
    } else {
        /* unpack the list of partially-coded superblocks */
        bit         = get_bits1(gb) ^ 1;
        current_run = 0;

        while (current_superblock < s->superblock_count && get_bits_left(gb) > 0) {
            if (s->theora && current_run == MAXIMUM_LONG_BIT_RUN)
                bit = get_bits1(gb);
            else
                bit ^= 1;

            current_run = get_vlc2(gb, s->superblock_run_length_vlc.table,
                                   6, 2) + 1;
            if (current_run == 34)
                current_run += get_bits(gb, 12);

            if (current_run > s->superblock_count - current_superblock) {
                av_log(s->avctx, AV_LOG_ERROR,
                       "Invalid partially coded superblock run length\n");
                return -1;
            }

            memset(s->superblock_coding + current_superblock, bit, current_run);

            current_superblock += current_run;
            if (bit)
                num_partial_superblocks += current_run;
        }

        /* unpack the list of fully coded superblocks if any of the blocks were
         * not marked as partially coded in the previous step */
        if (num_partial_superblocks < s->superblock_count) {
            int superblocks_decoded = 0;

            current_superblock = 0;
            bit                = get_bits1(gb) ^ 1;
            current_run        = 0;

            while (superblocks_decoded < s->superblock_count - num_partial_superblocks &&
                   get_bits_left(gb) > 0) {
                if (s->theora && current_run == MAXIMUM_LONG_BIT_RUN)
                    bit = get_bits1(gb);
                else
                    bit ^= 1;

                current_run = get_vlc2(gb, s->superblock_run_length_vlc.table,
                                       6, 2) + 1;
                if (current_run == 34)
                    current_run += get_bits(gb, 12);

                for (j = 0; j < current_run; current_superblock++) {
                    if (current_superblock >= s->superblock_count) {
                        av_log(s->avctx, AV_LOG_ERROR,
                               "Invalid fully coded superblock run length\n");
                        return -1;
                    }

                    /* skip any superblocks already marked as partially coded */
                    if (s->superblock_coding[current_superblock] == SB_NOT_CODED) {
                        s->superblock_coding[current_superblock] = 2 * bit;
                        j++;
                    }
                }
                superblocks_decoded += current_run;
            }
        }

        /* if there were partial blocks, initialize bitstream for
         * unpacking fragment codings */
        if (num_partial_superblocks) {
            current_run = 0;
            bit         = get_bits1(gb);
            /* toggle the bit because as soon as the first run length is
             * fetched the bit will be toggled again */
            bit ^= 1;
        }
    }

    /* figure out which fragments are coded; iterate through each
     * superblock (all planes) */
    s->total_num_coded_frags = 0;
    memset(s->macroblock_coding, MODE_COPY, s->macroblock_count);

    s->coded_fragment_list[0] = s->keyframe ? s->kf_coded_fragment_list
                                            : s->nkf_coded_fragment_list;

    for (plane = 0; plane < 3; plane++) {
        int sb_start = superblock_starts[plane];
        int sb_end   = sb_start + (plane ? s->c_superblock_count
                                         : s->y_superblock_count);
        int num_coded_frags = 0;

        if (s->keyframe) {
            if (s->num_kf_coded_fragment[plane] == -1) {
                for (i = sb_start; i < sb_end; i++) {
                    /* iterate through all 16 fragments in a superblock */
                    for (j = 0; j < 16; j++) {
                        /* if the fragment is in bounds, check its coding status */
                        current_fragment = s->superblock_fragments[i * 16 + j];
                        if (current_fragment != -1) {
                            s->coded_fragment_list[plane][num_coded_frags++] =
                                current_fragment;
                        }
                    }
                }
                s->num_kf_coded_fragment[plane] = num_coded_frags;
            } else
                num_coded_frags = s->num_kf_coded_fragment[plane];
        } else {
            for (i = sb_start; i < sb_end && get_bits_left(gb) > 0; i++) {
                if (get_bits_left(gb) < plane0_num_coded_frags >> 2) {
                    return AVERROR_INVALIDDATA;
                }
                /* iterate through all 16 fragments in a superblock */
                for (j = 0; j < 16; j++) {
                    /* if the fragment is in bounds, check its coding status */
                    current_fragment = s->superblock_fragments[i * 16 + j];
                    if (current_fragment != -1) {
                        int coded = s->superblock_coding[i];

                        if (coded == SB_PARTIALLY_CODED) {
                            /* fragment may or may not be coded; this is the case
                             * that cares about the fragment coding runs */
                            if (current_run-- == 0) {
                                bit        ^= 1;
                                current_run = get_vlc2(gb, s->fragment_run_length_vlc.table, 5, 2);
                            }
                            coded = bit;
                        }

                        if (coded) {
                            /* default mode; actual mode will be decoded in
                             * the next phase */
                            s->all_fragments[current_fragment].coding_method =
                                MODE_INTER_NO_MV;
                            s->coded_fragment_list[plane][num_coded_frags++] =
                                current_fragment;
                        } else {
                            /* not coded; copy this fragment from the prior frame */
                            s->all_fragments[current_fragment].coding_method =
                                MODE_COPY;
                        }
                    }
                }
            }
        }
        if (!plane)
            plane0_num_coded_frags = num_coded_frags;
        s->total_num_coded_frags += num_coded_frags;
        for (i = 0; i < 64; i++)
            s->num_coded_frags[plane][i] = num_coded_frags;
        if (plane < 2)
            s->coded_fragment_list[plane + 1] = s->coded_fragment_list[plane] +
                                                num_coded_frags;
    }
    return 0;
}

#define BLOCK_X (2 * mb_x + (k & 1))
#define BLOCK_Y (2 * mb_y + (k >> 1))

#if CONFIG_VP4_DECODER
/**
 * @return number of blocks, or > yuv_macroblock_count on error.
 *         return value is always >= 1.
 */
static int vp4_get_mb_count(Vp3DecodeContext *s, GetBitContext *gb)
{
    int v = 1;
    int bits;
    while ((bits = show_bits(gb, 9)) == 0x1ff) {
        skip_bits(gb, 9);
        v += 256;
        if (v > s->yuv_macroblock_count) {
            av_log(s->avctx, AV_LOG_ERROR, "Invalid run length\n");
            return v;
        }
    }
#define body(n) { \
    skip_bits(gb, 2 + n); \
    v += (1 << n) + get_bits(gb, n); }
#define thresh(n) (0x200 - (0x80 >> n))
#define else_if(n) else if (bits < thresh(n)) body(n)
    if (bits < 0x100) {
        skip_bits(gb, 1);
    } else if (bits < thresh(0)) {
        skip_bits(gb, 2);
        v += 1;
    }
    else_if(1)
    else_if(2)
    else_if(3)
    else_if(4)
    else_if(5)
    else_if(6)
    else body(7)
#undef body
#undef thresh
#undef else_if
    return v;
}

static int vp4_get_block_pattern(Vp3DecodeContext *s, GetBitContext *gb, int *next_block_pattern_table)
{
    int v = get_vlc2(gb, s->block_pattern_vlc[*next_block_pattern_table].table, 3, 2);
    if (v == -1) {
        av_log(s->avctx, AV_LOG_ERROR, "Invalid block pattern\n");
        *next_block_pattern_table = 0;
        return 0;
    }
    *next_block_pattern_table = vp4_block_pattern_table_selector[v];
    return v + 1;
}

static int vp4_unpack_macroblocks(Vp3DecodeContext *s, GetBitContext *gb)
{
    int plane, i, j, k, fragment;
    int next_block_pattern_table;
    int bit, current_run, has_partial;

    memset(s->macroblock_coding, MODE_COPY, s->macroblock_count);

    if (s->keyframe)
        return 0;

    has_partial = 0;
    bit         = get_bits1(gb);
    for (i = 0; i < s->yuv_macroblock_count; i += current_run) {
        if (get_bits_left(gb) <= 0)
            return AVERROR_INVALIDDATA;
        current_run = vp4_get_mb_count(s, gb);
        if (current_run > s->yuv_macroblock_count - i)
            return -1;
        memset(s->superblock_coding + i, 2 * bit, current_run);
        bit ^= 1;
        has_partial |= bit;
    }

    if (has_partial) {
        if (get_bits_left(gb) <= 0)
            return AVERROR_INVALIDDATA;
        bit  = get_bits1(gb);
        current_run = vp4_get_mb_count(s, gb);
        for (i = 0; i < s->yuv_macroblock_count; i++) {
            if (!s->superblock_coding[i]) {
                if (!current_run) {
                    bit ^= 1;
                    current_run = vp4_get_mb_count(s, gb);
                }
                s->superblock_coding[i] = bit;
                current_run--;
            }
        }
        if (current_run) /* handle situation when vp4_get_mb_count() fails */
            return -1;
    }

    next_block_pattern_table = 0;
    i = 0;
    for (plane = 0; plane < 3; plane++) {
        int sb_x, sb_y;
        int sb_width = plane ? s->c_superblock_width : s->y_superblock_width;
        int sb_height = plane ? s->c_superblock_height : s->y_superblock_height;
        int mb_width = plane ? s->c_macroblock_width : s->macroblock_width;
        int mb_height = plane ? s->c_macroblock_height : s->macroblock_height;
        int fragment_width = s->fragment_width[!!plane];
        int fragment_height = s->fragment_height[!!plane];

        for (sb_y = 0; sb_y < sb_height; sb_y++) {
            for (sb_x = 0; sb_x < sb_width; sb_x++) {
                for (j = 0; j < 4; j++) {
                    int mb_x = 2 * sb_x + (j >> 1);
                    int mb_y = 2 * sb_y + (j >> 1) ^ (j & 1);
                    int mb_coded, pattern, coded;

                    if (mb_x >= mb_width || mb_y >= mb_height)
                        continue;

                    mb_coded = s->superblock_coding[i++];

                    if (mb_coded == SB_FULLY_CODED)
                        pattern = 0xF;
                    else if (mb_coded == SB_PARTIALLY_CODED)
                        pattern = vp4_get_block_pattern(s, gb, &next_block_pattern_table);
                    else
                        pattern = 0;

                    for (k = 0; k < 4; k++) {
                        if (BLOCK_X >= fragment_width || BLOCK_Y >= fragment_height)
                            continue;
                        fragment = s->fragment_start[plane] + BLOCK_Y * fragment_width + BLOCK_X;
                        coded = pattern & (8 >> k);
                        /* MODE_INTER_NO_MV is the default for coded fragments.
                           the actual method is decoded in the next phase. */
                        s->all_fragments[fragment].coding_method = coded ? MODE_INTER_NO_MV : MODE_COPY;
                    }
                }
            }
        }
    }
    return 0;
}
#endif

/*
 * This function unpacks all the coding mode data for individual macroblocks
 * from the bitstream.
 */
static int unpack_modes(Vp3DecodeContext *s, GetBitContext *gb)
{
    int i, j, k, sb_x, sb_y;
    int scheme;
    int current_macroblock;
    int current_fragment;
    int coding_mode;
    int custom_mode_alphabet[CODING_MODE_COUNT];
    const int *alphabet;
    Vp3Fragment *frag;

    if (s->keyframe) {
        for (i = 0; i < s->fragment_count; i++)
            s->all_fragments[i].coding_method = MODE_INTRA;
    } else {
        /* fetch the mode coding scheme for this frame */
        scheme = get_bits(gb, 3);

        /* is it a custom coding scheme? */
        if (scheme == 0) {
            for (i = 0; i < 8; i++)
                custom_mode_alphabet[i] = MODE_INTER_NO_MV;
            for (i = 0; i < 8; i++)
                custom_mode_alphabet[get_bits(gb, 3)] = i;
            alphabet = custom_mode_alphabet;
        } else
            alphabet = ModeAlphabet[scheme - 1];

        /* iterate through all of the macroblocks that contain 1 or more
         * coded fragments */
        for (sb_y = 0; sb_y < s->y_superblock_height; sb_y++) {
            for (sb_x = 0; sb_x < s->y_superblock_width; sb_x++) {
                if (get_bits_left(gb) <= 0)
                    return -1;

                for (j = 0; j < 4; j++) {
                    int mb_x = 2 * sb_x + (j >> 1);
                    int mb_y = 2 * sb_y + (((j >> 1) + j) & 1);
                    current_macroblock = mb_y * s->macroblock_width + mb_x;

                    if (mb_x >= s->macroblock_width ||
                        mb_y >= s->macroblock_height)
                        continue;

                    /* coding modes are only stored if the macroblock has
                     * at least one luma block coded, otherwise it must be
                     * INTER_NO_MV */
                    for (k = 0; k < 4; k++) {
                        current_fragment = BLOCK_Y *
                                           s->fragment_width[0] + BLOCK_X;
                        if (s->all_fragments[current_fragment].coding_method != MODE_COPY)
                            break;
                    }
                    if (k == 4) {
                        s->macroblock_coding[current_macroblock] = MODE_INTER_NO_MV;
                        continue;
                    }

                    /* mode 7 means get 3 bits for each coding mode */
                    if (scheme == 7)
                        coding_mode = get_bits(gb, 3);
                    else
                        coding_mode = alphabet[get_vlc2(gb, s->mode_code_vlc.table, 3, 3)];

                    s->macroblock_coding[current_macroblock] = coding_mode;
                    for (k = 0; k < 4; k++) {
                        frag = s->all_fragments + BLOCK_Y * s->fragment_width[0] + BLOCK_X;
                        if (frag->coding_method != MODE_COPY)
                            frag->coding_method = coding_mode;
                    }

#define SET_CHROMA_MODES                                                      \
    if (frag[s->fragment_start[1]].coding_method != MODE_COPY)                \
        frag[s->fragment_start[1]].coding_method = coding_mode;               \
    if (frag[s->fragment_start[2]].coding_method != MODE_COPY)                \
        frag[s->fragment_start[2]].coding_method = coding_mode;

                    if (s->chroma_y_shift) {
                        frag = s->all_fragments + mb_y *
                               s->fragment_width[1] + mb_x;
                        SET_CHROMA_MODES
                    } else if (s->chroma_x_shift) {
                        frag = s->all_fragments +
                               2 * mb_y * s->fragment_width[1] + mb_x;
                        for (k = 0; k < 2; k++) {
                            SET_CHROMA_MODES
                            frag += s->fragment_width[1];
                        }
                    } else {
                        for (k = 0; k < 4; k++) {
                            frag = s->all_fragments +
                                   BLOCK_Y * s->fragment_width[1] + BLOCK_X;
                            SET_CHROMA_MODES
                        }
                    }
                }
            }
        }
    }

    return 0;
}

static int vp4_get_mv(Vp3DecodeContext *s, GetBitContext *gb, int axis, int last_motion)
{
    int v = get_vlc2(gb, s->vp4_mv_vlc[axis][vp4_mv_table_selector[FFABS(last_motion)]].table, 6, 2) - 31;
    return last_motion < 0 ? -v : v;
}

/*
 * This function unpacks all the motion vectors for the individual
 * macroblocks from the bitstream.
 */
static int unpack_vectors(Vp3DecodeContext *s, GetBitContext *gb)
{
    int j, k, sb_x, sb_y;
    int coding_mode;
    int motion_x[4];
    int motion_y[4];
    int last_motion_x = 0;
    int last_motion_y = 0;
    int prior_last_motion_x = 0;
    int prior_last_motion_y = 0;
    int last_gold_motion_x = 0;
    int last_gold_motion_y = 0;
    int current_macroblock;
    int current_fragment;
    int frag;

    if (s->keyframe)
        return 0;

    /* coding mode 0 is the VLC scheme; 1 is the fixed code scheme; 2 is VP4 code scheme */
    coding_mode = s->version < 2 ? get_bits1(gb) : 2;

    /* iterate through all of the macroblocks that contain 1 or more
     * coded fragments */
    for (sb_y = 0; sb_y < s->y_superblock_height; sb_y++) {
        for (sb_x = 0; sb_x < s->y_superblock_width; sb_x++) {
            if (get_bits_left(gb) <= 0)
                return -1;

            for (j = 0; j < 4; j++) {
                int mb_x = 2 * sb_x + (j >> 1);
                int mb_y = 2 * sb_y + (((j >> 1) + j) & 1);
                current_macroblock = mb_y * s->macroblock_width + mb_x;

                if (mb_x >= s->macroblock_width  ||
                    mb_y >= s->macroblock_height ||
                    s->macroblock_coding[current_macroblock] == MODE_COPY)
                    continue;

                switch (s->macroblock_coding[current_macroblock]) {
                case MODE_GOLDEN_MV:
                    if (coding_mode == 2) { /* VP4 */
                        last_gold_motion_x = motion_x[0] = vp4_get_mv(s, gb, 0, last_gold_motion_x);
                        last_gold_motion_y = motion_y[0] = vp4_get_mv(s, gb, 1, last_gold_motion_y);
                        break;
                    } /* otherwise fall through */
                case MODE_INTER_PLUS_MV:
                    /* all 6 fragments use the same motion vector */
                    if (coding_mode == 0) {
                        motion_x[0] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
                        motion_y[0] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
                    } else if (coding_mode == 1) {
                        motion_x[0] = fixed_motion_vector_table[get_bits(gb, 6)];
                        motion_y[0] = fixed_motion_vector_table[get_bits(gb, 6)];
                    } else { /* VP4 */
                        motion_x[0] = vp4_get_mv(s, gb, 0, last_motion_x);
                        motion_y[0] = vp4_get_mv(s, gb, 1, last_motion_y);
                    }

                    /* vector maintenance, only on MODE_INTER_PLUS_MV */
                    if (s->macroblock_coding[current_macroblock] == MODE_INTER_PLUS_MV) {
                        prior_last_motion_x = last_motion_x;
                        prior_last_motion_y = last_motion_y;
                        last_motion_x       = motion_x[0];
                        last_motion_y       = motion_y[0];
                    }
                    break;

                case MODE_INTER_FOURMV:
                    /* vector maintenance */
                    prior_last_motion_x = last_motion_x;
                    prior_last_motion_y = last_motion_y;

                    /* fetch 4 vectors from the bitstream, one for each
                     * Y fragment, then average for the C fragment vectors */
                    for (k = 0; k < 4; k++) {
                        current_fragment = BLOCK_Y * s->fragment_width[0] + BLOCK_X;
                        if (s->all_fragments[current_fragment].coding_method != MODE_COPY) {
                            if (coding_mode == 0) {
                                motion_x[k] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
                                motion_y[k] = motion_vector_table[get_vlc2(gb, s->motion_vector_vlc.table, 6, 2)];
                            } else if (coding_mode == 1) {
                                motion_x[k] = fixed_motion_vector_table[get_bits(gb, 6)];
                                motion_y[k] = fixed_motion_vector_table[get_bits(gb, 6)];
                            } else { /* VP4 */
                                motion_x[k] = vp4_get_mv(s, gb, 0, prior_last_motion_x);
                                motion_y[k] = vp4_get_mv(s, gb, 1, prior_last_motion_y);
                            }
                            last_motion_x = motion_x[k];
                            last_motion_y = motion_y[k];
                        } else {
                            motion_x[k] = 0;
                            motion_y[k] = 0;
                        }
                    }
                    break;

                case MODE_INTER_LAST_MV:
                    /* all 6 fragments use the last motion vector */
                    motion_x[0] = last_motion_x;
                    motion_y[0] = last_motion_y;

                    /* no vector maintenance (last vector remains the
                     * last vector) */
                    break;

                case MODE_INTER_PRIOR_LAST:
                    /* all 6 fragments use the motion vector prior to the
                     * last motion vector */
                    motion_x[0] = prior_last_motion_x;
                    motion_y[0] = prior_last_motion_y;

                    /* vector maintenance */
                    prior_last_motion_x = last_motion_x;
                    prior_last_motion_y = last_motion_y;
                    last_motion_x       = motion_x[0];
                    last_motion_y       = motion_y[0];
                    break;

                default:
                    /* covers intra, inter without MV, golden without MV */
                    motion_x[0] = 0;
                    motion_y[0] = 0;

                    /* no vector maintenance */
                    break;
                }

                /* assign the motion vectors to the correct fragments */
                for (k = 0; k < 4; k++) {
                    current_fragment =
                        BLOCK_Y * s->fragment_width[0] + BLOCK_X;
                    if (s->macroblock_coding[current_macroblock] == MODE_INTER_FOURMV) {
                        s->motion_val[0][current_fragment][0] = motion_x[k];
                        s->motion_val[0][current_fragment][1] = motion_y[k];
                    } else {
                        s->motion_val[0][current_fragment][0] = motion_x[0];
                        s->motion_val[0][current_fragment][1] = motion_y[0];
                    }
                }

                if (s->chroma_y_shift) {
                    if (s->macroblock_coding[current_macroblock] == MODE_INTER_FOURMV) {
                        motion_x[0] = RSHIFT(motion_x[0] + motion_x[1] +
                                             motion_x[2] + motion_x[3], 2);
                        motion_y[0] = RSHIFT(motion_y[0] + motion_y[1] +
                                             motion_y[2] + motion_y[3], 2);
                    }
                    if (s->version <= 2) {
                        motion_x[0] = (motion_x[0] >> 1) | (motion_x[0] & 1);
                        motion_y[0] = (motion_y[0] >> 1) | (motion_y[0] & 1);
                    }
                    frag = mb_y * s->fragment_width[1] + mb_x;
                    s->motion_val[1][frag][0] = motion_x[0];
                    s->motion_val[1][frag][1] = motion_y[0];
                } else if (s->chroma_x_shift) {
                    if (s->macroblock_coding[current_macroblock] == MODE_INTER_FOURMV) {
                        motion_x[0] = RSHIFT(motion_x[0] + motion_x[1], 1);
                        motion_y[0] = RSHIFT(motion_y[0] + motion_y[1], 1);
                        motion_x[1] = RSHIFT(motion_x[2] + motion_x[3], 1);
                        motion_y[1] = RSHIFT(motion_y[2] + motion_y[3], 1);
                    } else {
                        motion_x[1] = motion_x[0];
                        motion_y[1] = motion_y[0];
                    }
                    if (s->version <= 2) {
                        motion_x[0] = (motion_x[0] >> 1) | (motion_x[0] & 1);
                        motion_x[1] = (motion_x[1] >> 1) | (motion_x[1] & 1);
                    }
                    frag = 2 * mb_y * s->fragment_width[1] + mb_x;
                    for (k = 0; k < 2; k++) {
                        s->motion_val[1][frag][0] = motion_x[k];
                        s->motion_val[1][frag][1] = motion_y[k];
                        frag += s->fragment_width[1];
                    }
                } else {
                    for (k = 0; k < 4; k++) {
                        frag = BLOCK_Y * s->fragment_width[1] + BLOCK_X;
                        if (s->macroblock_coding[current_macroblock] == MODE_INTER_FOURMV) {
                            s->motion_val[1][frag][0] = motion_x[k];
                            s->motion_val[1][frag][1] = motion_y[k];
                        } else {
                            s->motion_val[1][frag][0] = motion_x[0];
                            s->motion_val[1][frag][1] = motion_y[0];
                        }
                    }
                }
            }
        }
    }

    return 0;
}

static int unpack_block_qpis(Vp3DecodeContext *s, GetBitContext *gb)
{
    int qpi, i, j, bit, run_length, blocks_decoded, num_blocks_at_qpi;
    int num_blocks = s->total_num_coded_frags;

    for (qpi = 0; qpi < s->nqps - 1 && num_blocks > 0; qpi++) {
        i = blocks_decoded = num_blocks_at_qpi = 0;

        bit        = get_bits1(gb) ^ 1;
        run_length = 0;

        do {
            if (run_length == MAXIMUM_LONG_BIT_RUN)
                bit = get_bits1(gb);
            else
                bit ^= 1;

            run_length = get_vlc2(gb, s->superblock_run_length_vlc.table, 6, 2) + 1;
            if (run_length == 34)
                run_length += get_bits(gb, 12);
            blocks_decoded += run_length;

            if (!bit)
                num_blocks_at_qpi += run_length;

            for (j = 0; j < run_length; i++) {
                if (i >= s->total_num_coded_frags)
                    return -1;

                if (s->all_fragments[s->coded_fragment_list[0][i]].qpi == qpi) {
                    s->all_fragments[s->coded_fragment_list[0][i]].qpi += bit;
                    j++;
                }
            }
        } while (blocks_decoded < num_blocks && get_bits_left(gb) > 0);

        num_blocks -= num_blocks_at_qpi;
    }

    return 0;
}

static inline int get_eob_run(GetBitContext *gb, int token)
{
    int v = eob_run_table[token].base;
    if (eob_run_table[token].bits)
        v += get_bits(gb, eob_run_table[token].bits);
    return v;
}

static inline int get_coeff(GetBitContext *gb, int token, int16_t *coeff)
{
    int bits_to_get, zero_run;

    bits_to_get = coeff_get_bits[token];
    if (bits_to_get)
        bits_to_get = get_bits(gb, bits_to_get);
    *coeff = coeff_tables[token][bits_to_get];

    zero_run = zero_run_base[token];
    if (zero_run_get_bits[token])
        zero_run += get_bits(gb, zero_run_get_bits[token]);

    return zero_run;
}

/*
 * This function is called by unpack_dct_coeffs() to extract the VLCs from
 * the bitstream. The VLCs encode tokens which are used to unpack DCT
 * data. This function unpacks all the VLCs for either the Y plane or both
 * C planes, and is called for DC coefficients or different AC coefficient
 * levels (since different coefficient types require different VLC tables.
 *
 * This function returns a residual eob run. E.g, if a particular token gave
 * instructions to EOB the next 5 fragments and there were only 2 fragments
 * left in the current fragment range, 3 would be returned so that it could
 * be passed into the next call to this same function.
 */
static int unpack_vlcs(Vp3DecodeContext *s, GetBitContext *gb,
                       VLC *table, int coeff_index,
                       int plane,
                       int eob_run)
{
    int i, j = 0;
    int token;
    int zero_run  = 0;
    int16_t coeff = 0;
    int blocks_ended;
    int coeff_i = 0;
    int num_coeffs      = s->num_coded_frags[plane][coeff_index];
    int16_t *dct_tokens = s->dct_tokens[plane][coeff_index];

    /* local references to structure members to avoid repeated dereferences */
    int *coded_fragment_list   = s->coded_fragment_list[plane];
    Vp3Fragment *all_fragments = s->all_fragments;
    VLC_TYPE(*vlc_table)[2] = table->table;

    if (num_coeffs < 0) {
        av_log(s->avctx, AV_LOG_ERROR,
               "Invalid number of coefficients at level %d\n", coeff_index);
        return AVERROR_INVALIDDATA;
    }

    if (eob_run > num_coeffs) {
        coeff_i      =
        blocks_ended = num_coeffs;
        eob_run     -= num_coeffs;
    } else {
        coeff_i      =
        blocks_ended = eob_run;
        eob_run      = 0;
    }

    // insert fake EOB token to cover the split between planes or zzi
    if (blocks_ended)
        dct_tokens[j++] = blocks_ended << 2;

    while (coeff_i < num_coeffs && get_bits_left(gb) > 0) {
        /* decode a VLC into a token */
        token = get_vlc2(gb, vlc_table, 11, 3);
        /* use the token to get a zero run, a coefficient, and an eob run */
        if ((unsigned) token <= 6U) {
            eob_run = get_eob_run(gb, token);
            if (!eob_run)
                eob_run = INT_MAX;

            // record only the number of blocks ended in this plane,
            // any spill will be recorded in the next plane.
            if (eob_run > num_coeffs - coeff_i) {
                dct_tokens[j++] = TOKEN_EOB(num_coeffs - coeff_i);
                blocks_ended   += num_coeffs - coeff_i;
                eob_run        -= num_coeffs - coeff_i;
                coeff_i         = num_coeffs;
            } else {
                dct_tokens[j++] = TOKEN_EOB(eob_run);
                blocks_ended   += eob_run;
                coeff_i        += eob_run;
                eob_run         = 0;
            }
        } else if (token >= 0) {
            zero_run = get_coeff(gb, token, &coeff);

            if (zero_run) {
                dct_tokens[j++] = TOKEN_ZERO_RUN(coeff, zero_run);
            } else {
                // Save DC into the fragment structure. DC prediction is
                // done in raster order, so the actual DC can't be in with
                // other tokens. We still need the token in dct_tokens[]
                // however, or else the structure collapses on itself.
                if (!coeff_index)
                    all_fragments[coded_fragment_list[coeff_i]].dc = coeff;

                dct_tokens[j++] = TOKEN_COEFF(coeff);
            }

            if (coeff_index + zero_run > 64) {
                av_log(s->avctx, AV_LOG_DEBUG,
                       "Invalid zero run of %d with %d coeffs left\n",
                       zero_run, 64 - coeff_index);
                zero_run = 64 - coeff_index;
            }

            // zero runs code multiple coefficients,
            // so don't try to decode coeffs for those higher levels
            for (i = coeff_index + 1; i <= coeff_index + zero_run; i++)
                s->num_coded_frags[plane][i]--;
            coeff_i++;
        } else {
            av_log(s->avctx, AV_LOG_ERROR, "Invalid token %d\n", token);
            return -1;
        }
    }

    if (blocks_ended > s->num_coded_frags[plane][coeff_index])
        av_log(s->avctx, AV_LOG_ERROR, "More blocks ended than coded!\n");

    // decrement the number of blocks that have higher coefficients for each
    // EOB run at this level
    if (blocks_ended)
        for (i = coeff_index + 1; i < 64; i++)
            s->num_coded_frags[plane][i] -= blocks_ended;

    // setup the next buffer
    if (plane < 2)
        s->dct_tokens[plane + 1][coeff_index] = dct_tokens + j;
    else if (coeff_index < 63)
        s->dct_tokens[0][coeff_index + 1] = dct_tokens + j;

    return eob_run;
}

static void reverse_dc_prediction(Vp3DecodeContext *s,
                                  int first_fragment,
                                  int fragment_width,
                                  int fragment_height);
/*
 * This function unpacks all of the DCT coefficient data from the
 * bitstream.
 */
static int unpack_dct_coeffs(Vp3DecodeContext *s, GetBitContext *gb)
{
    int i;
    int dc_y_table;
    int dc_c_table;
    int ac_y_table;
    int ac_c_table;
    int residual_eob_run = 0;
    VLC *y_tables[64];
    VLC *c_tables[64];

    s->dct_tokens[0][0] = s->dct_tokens_base;

    if (get_bits_left(gb) < 16)
        return AVERROR_INVALIDDATA;

    /* fetch the DC table indexes */
    dc_y_table = get_bits(gb, 4);
    dc_c_table = get_bits(gb, 4);

    /* unpack the Y plane DC coefficients */
    residual_eob_run = unpack_vlcs(s, gb, &s->dc_vlc[dc_y_table], 0,
                                   0, residual_eob_run);
    if (residual_eob_run < 0)
        return residual_eob_run;
    if (get_bits_left(gb) < 8)
        return AVERROR_INVALIDDATA;

    /* reverse prediction of the Y-plane DC coefficients */
    reverse_dc_prediction(s, 0, s->fragment_width[0], s->fragment_height[0]);

    /* unpack the C plane DC coefficients */
    residual_eob_run = unpack_vlcs(s, gb, &s->dc_vlc[dc_c_table], 0,
                                   1, residual_eob_run);
    if (residual_eob_run < 0)
        return residual_eob_run;
    residual_eob_run = unpack_vlcs(s, gb, &s->dc_vlc[dc_c_table], 0,
                                   2, residual_eob_run);
    if (residual_eob_run < 0)
        return residual_eob_run;

    /* reverse prediction of the C-plane DC coefficients */
    if (!(s->avctx->flags & AV_CODEC_FLAG_GRAY)) {
        reverse_dc_prediction(s, s->fragment_start[1],
                              s->fragment_width[1], s->fragment_height[1]);
        reverse_dc_prediction(s, s->fragment_start[2],
                              s->fragment_width[1], s->fragment_height[1]);
    }

    if (get_bits_left(gb) < 8)
        return AVERROR_INVALIDDATA;
    /* fetch the AC table indexes */
    ac_y_table = get_bits(gb, 4);
    ac_c_table = get_bits(gb, 4);

    /* build tables of AC VLC tables */
    for (i = 1; i <= 5; i++) {
        y_tables[i] = &s->ac_vlc_1[ac_y_table];
        c_tables[i] = &s->ac_vlc_1[ac_c_table];
    }
    for (i = 6; i <= 14; i++) {
        y_tables[i] = &s->ac_vlc_2[ac_y_table];
        c_tables[i] = &s->ac_vlc_2[ac_c_table];
    }
    for (i = 15; i <= 27; i++) {
        y_tables[…